Preparation of linear halosiloxanes and compounds derived therefrom

ABSTRACT

A PROCESS FOR PREPARING LINEAR HALOSILOXANE POLYMERS BY THE REDISTRIBUTION OF HALOSILOXANES OR A HALOSILOXANE WITH CYCLOSTRISILOXANE OR CYCLOTETRASILOXANE IN THE PRESENCE OF A BASIC CATALYST SUCH AS THE PHOSPHINE OXIDES OR AMINE OXIDES AS WELL AS NOVEL LINEAR HALO ENDBLOCKED SILOXANE POLYMERS. THE LINEAR HALOSILOXANE POLYMERS FIND UTILITY IN THE PREPARATION OF HEAT CURABLE RESINS AND ELASTOMERS.

United States Patent ABSTRACT OF THE DISCLOSURE A process for preparinglinear halosiloxane polymers by the redistribution of halosiloxanes or ahalosiloxane with cyclotrisiloxane or cyclotet-rasiloxane in thepresence of a basic catalyst such. as the phosphine oxides or amineoxides as well as novel linear halo endblocked siloxane polymers. Thelinear halosiloxane polymers find utility in the preparation of heatcurable resins .and elastomers.

BACKGROUND OF THE INVENTION This invention relates'to a process forproducing linear halosiloxane .polymers. More particularly thisinvention relates to a process for preparing linear halosiloxanepolymers throughthe redistribution of halosilanes with cyclosiloxanecompounds andto novel linear halo endblocked siloxanes, k

Heretofore, linear halosiloxane polymers have been prepared byequilibrium, reactions of halosilanes with organopolysiloxanes. However,such types of processes have undesirable features, for example, reactionconditions are oftenso severe as to cause cleavage of certain radicals,such as phenyl and vinyl radicals from the silicon atoms. Moreover, theuse of catalysts, such as hydrogen halides or Lewis acids can lead torearrangement of the SiOSi bonds of the polymer as well as cleavage ofsuch organic radicals from the silicon atoms of the reactants. Morerecently it has been proposed that the above drawbacks may be overcomeby preparing linear halosiloxane polymers through the redistribution ofhalosilanes with cyclotrisiloxane in the absence or presence of an amineor amine salt catalyst, as witnessed by U.S. Pat. 3,162,662. However,this known procedure is restricted to the use of only cyclotrisiloxanesgSUMMARY OF THE INVENTION It has-now been discovered that the abovedisadvantages can be overcome and that linear halosiloxane polymersmaybe obtained-through the redistribution of halosilanes withcyclotrisiloxane or cyclotetrasiloxane in the presence of a phosphineoxide or amine oxide catalyst.

Therefore it is an object of this invention to provide an efficient andeconomical process for preparing linear halosiloxane polymers It is alsoan object to provide a process for selectively preparing low molecularweight halosiloxane polymersin. high yields, Another object is toprovide novel low molecular weight short-chain halosiloxane compounds.Otherobjects and advantages of this invention .will become-readilyapparentfrom the following description and appended claims, '5 Morespecifically, .one process aspect of the instant inventionmaybedescribed as a method for preparing low molecular weight linearhalopolysiloxanes which comprisesinterreacting, in the presence of acatalytic amount of a basic catalyst selected from the group consistingof phosphine oxides, amine oxides or mixtures thereof, (A)-anorganocyclosiloxane having the formula wherein eachRisradicaLindependently selected from the group consisting of a hydrogenatom, monovalent hydrocarbon radicals and monovalent substitutedhydrocarbon radicals and wherein n is an integer of 3 or 4, with (B) ahalosilane having the formula RmSiX wherein each R is the same asdefined above, each X is a halogen atom and m has a value of from 0 to 3inclusive; whereby the cyclicsiloxane forms a linear siloxane polymerhaving attached to one of its terminal silicon atoms a halogen atom fromthe silane and having attached to its other terminal silicon atomthrough a siloxane linkage the silicon atom of the silane from which thehalogen atom separated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cyclosiloxanes which can beused in the redistribution process of this invention includecyclotrisiloxanes, [R SiO] as well as cyclotetrasiloxanes, [R SiO]wherein each R radical of said cyclosiloxanes independently represents aradical selected from the group consisting of a hydrogen atom, amonovalent hydrocarbon radical having from 1 to 18 carbon atoms and asubstituted monovalent hydrocarbon radical. Such cyclosiloxanes as wellas methods for their preparation are Well known in the art. Illustrativeexamples of such monovalent hydrocarbon radicals are alkyl radicals suchas methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl,Z-ethylhexyl, decyl, dodecyl, octadecyl and the like; alkenyl radicalssuch as vinyl, allyl, hexadienyl and the like; aryl radicals such as,phenyl, naphthyl and the like; alkaryl radicals such as methylphenyl,dimethylphenyl and the like; aralkyl radicals, such as benzl,phenylethyl and the like; cycloalkyl radicals such as cyclopentyl,cyclohexl and the like and cycloalkenyl radicals such as, cyclopentenyl,cyclohexenyl and the like. Illustrative substituents that may be carriedby the above hydrocarbon radicals include halogen, cyano, acyloxyradicals and the like. Such types of substituted hydrocarbons that maybe mentioned are 2,4,6-trichlorobenzyl, chlorophenyl, beta-cyanoethyl,gamma-cyanopropyl, gamma-chloropropyl gamma-methacrloxypropyl and thelike. Preferably each R individually represents a radical selected fromthe group consisting of hydrogen, methyl, ethyl, vinyl, and phenylradicals and most preferably every R is a methyl or ethyl radical. Amongthe preferred cyclosiloxanes that may be mentioned arehexamethyltrisiloxane, octamethyltetrasiloxane, and the like. The morepreferred compounds are the cyclotetrasiloxanes, especiallyoctamethyltetrasiloxane.

The halosilanes which are employable in the redistribution of thisinvention include any silane having from one, two, three or four halogenatoms and having the formula wherein each R is the same as definedabove, m has a value of from (I to 3 inclusive and each X represents ahalogen atom such as chlorine, bromine, iodine and fluorine, withchlorine being the most preferred. Such halosilanes as well as methodsfor their preparation are well known in the art. Illustrative examplesof such silane compounds include those of the formulas, SiCl HSiCl RSiClH SiCl R SiCl RHSICIg, H SiCl, R SiCl, RHzSICI and R HSiCI Where each Ris a monovalent or substituted monovalent hydrocarbon radical as definedabove. Among the more preferred chlorosilanes that may be mentioned areSiCl MeSiCl EtSiC1 Me SiCl MeEtSiCl MeSiCl SiCl Et SiCl Me SiCl, EtSiCl, Me I-ISiCl, CN,(,CH SiMe'Cl CN(CH SiMeCl CN (CH SiMeCl CN (CH SiClCl( CH SiMeCl Cl CH SiMeCl Br (CH SiMeCl MeO (CH SiMeCl,

MeO(CH SiMeCl MeSiCl SiCl C H SiMeCl ClSiCl MeViSiCl ViSiCl; and thelike. The most preferred chlorosilanes are the dichlorosilanes,especially Me SiCI In the above formulas and throughout the rest of thisdisclosure Me represents a methyl (CH radical; Et represents an ethyl(-C H radical and 4: represents a phenyl (C H radical, Vi represents avinyl (--CI-I=CH) radical.

As pointed out above the redistribution process of this invention mustbe carried out in the presence of a basic catalyst such as a phosphineoxide, an amine oxide, or mixtures of said oxide compounds. Theexpression phosphine oxide as used therein encompasses any compoundcontaining an oxygen atom solely and directly attached to the phosphorusatom. Such phosphine oxides as well as methods for their preparation arewell known in the art, as shown in Organophosphorus Compounds byKosolapoff (1950) published by I. Wiley & Sons Inc., New York.Illustrative examples of such phosphine oxides include 3 a)3 4 9)a 2( 49) 4 9)2 z)3 8 1'l)3 z )3 (Me N) PO-SiCl,,

I] ll (Cl nhP (CH2)2 4 9):

and the like. The symbols Me and are the same as defined above. Thepreferred phosphine oxide catalysts have the formula R PO wherein each Rindividually represents a radical selected from the group consisting ofalkyl having from 1 to 8 carbon atoms, phenyl and dimethylaminoradicals, especially PO, (n-C H PO and [(CH N] P=O. The expression amineoxide as used herein incompasses any compound containing an oxygen atomsolely and directly attached to a nitrogen atom. Such amine oxides aswell as methods for their preparation are well known in the art, asshown in Advanced Organic Chemistry by Fusyon (1950), published by J.Wiley & Sons Inc., New York.

The preferred amine oxide catalysts have the formula R NO wherein each Rindividually represents a monovalent hydrocarbon radical having from 1to 8 carbon atoms and selected from the group consisting of alkyl, aryl,alkaryl, aralkyl and cycloalkyl radicals, such as methyl, ethyl, propyl,isopropyl, butyl, tert-butyl, 2-ethylhexyl, octyl, phenyl, benzyl,toluene, cyclohexyl and the like, or each R and N taken collectively canform a heterocyclic ring structure such as pyridine and the like.Illustrative examples of some of the more preferred amine oxidesinclude, pyridine N-oxide, 2,6-dimethylpyridine N-oxide,4-methylpyridine N-oxide, 2-methylpyridine N-oxide, 4- cyanopyridineN-oxide, triphenyl N-oxide and the trialkyl N-oxides having from 1 to 8carbon atoms such as trimethyl N-oxide, triethyl N-oxide, tributylN-oxide, trioctyl N-oxide and the like.

The amount of catalyst employed is not critical for it obviously needonly be a catalytic amount. Generally amounts of catalysts ranging fromabout 0.1 to about 2 percent by weight based on the total weight ofsilicon reactants employed will be sufficient although more than about 2percent by weight of catalyst can be employed if desired.

In the redistribution reaction of this invention the general feature isthe interreaction of the chlorosilane with the cyclosiloxane whereby thecyclosiloxane chain is split so that it is converted to a linearsiloxane polymer having attached to one of its terminal silicon atoms achlorine 4 atom from the chlorosilane starting material and havingattached to its other terminal silicon atom through a siloxane linkagethe silicon atom of said silane from which the chlorine atom separated.This general reaction can be described by the following illustrativeequation.

wherein m, n and each R is the same as defined above. Along with themore preferred chlorosiloxane products containing four or five siliconatoms per molecule as outlined above, further redistribution sideproducts such as the longer chain linear chlorosiloxane polymers forexample, and the like where each R is the same as defined above and x is3 or 4 or higher may result. Note the cyclotrisiloxane redistribution inU.S. Pat. 3,162,662. Thus, the complex interplay of recognizedparameters, such as the compounds involved in the process, theirindividual reactivity, process conditions, etc., all elfects the courseof the redistribution and the extent and amount of desired Si, or Sisilicon polymers and side-products produced. Accordingly, the instantprocess now makes it possible to produce low molecular weightchlorosiloxane polymers containing four or five silicon atoms permolecule in very good yields by coordinating said parameters underredistribution conditions sufficiently slow enough so thatthe desiredspecific products can be isolated and obtained before furtherredistribtuion and/or equilibration has occurred. The mole ratio ofchlorosilane to the cyclicsiloxane employed is not critical and merelydepends on the reactivity of the compounds employed and the type ofproduct desired. For example, in general the higher the reaction rate,the higher the ratio of cyclic to silane or the greater the reactivityof the cyclic over the silane, the lower the amount of the specificlinear chlorosiloxane Si; or Si polymers obtained due to the productionof more side-products. For instance, in general the cyclotrisiloxanesare more reactive than the cyclotetrasiloxanes and the reactivity of thechlorosilanes is increased as one goes from a monochlorosilane to atetrachlorosilane. Accordingly, by way of a specific example about a 1:1mole ratio reaction of a monochlorosilane to a cyclotrisiloxane willnormally produce a sizeable mixture of linear chlorosiloxane productsdue to the low reactivity of the monochlorosilane to cyclotrisiloxane.However, this may be olf-set and a greater yield of the specific linearchlorosiloxane Si polymer obtained by increasing the amount ofmonochlorosilane above that of the 1:1 mole ratio. Accordingly, the moleratio is not critical but basically dependent only upon whether onewishes to obtain a mixture of related products or a high yield of aspecific product. The same is true of the temperature and time of thereaction. The reaction temperature of this invention can range from roomtemperature up to 150 C. or higher, however, temperatures ranging fromabout 20 C. to C. are generally preferred. The longer the reaction timethe greater the possibility of further redistribution to additionallinear chlorosiloxanes other than the specific Si, or Si polymers. Whenhigh yields of these specific polymers are desired the reaction time isgoverned by analytical monitoring. Moreover, when mixtures of difierentchlorosiloxane polymers are obtained they may be employed as such or theindividual classes of siloxanes may be conveniently separated andrecovered if desired by such conventional methods as distillation, vaporphase chromatography and the like. Of course, it should also beunderstood if desired one may employ a mixture of such halosilanesand/or a mixture of the tri and tetracyclics reactants in the sameredistribution process, although such is not generally preferred.

Another novel feature of the instant invention is the discovery of twodistinct methods for the production of novel linear chlorosiloxanepolymers having the formula wherein eachR is the same as defined above.It has been surprisingly found that these novel polymers may be produceddirectly by the redistribution process which comprises interreacting, inthe presence of a catalytic amount of a basic catalyst selected from thegroup consisting of phosphine oxides, amine oxides, or mixtures thereof,said catalysts having been described above, at about 90 C., atetrachlorosilane with a cyclotrisiloxane of the formula [R SiO] whereineach R is the same as defined above, and wherein the mole ratio ofsilane to cyclic is about 1:1. For example, the redistribution reactionof about a 1:1 mole ratio of tetrachlorosilane withhexamethyltritrisiloxane at about 90 C. in the catalytic presence of (MeN) PO produces a good yield of a linear1,3,3,7-tetrachlorohexamethylsiloxane polymer of the formula Thisprocess is indeed-surprising since the same example carried out underidentical conditions but at a lower temperature for instance at roomtemperature produces a linear 1,1,1,7 tetrachlorohexamethylsiloxanepolymer product of the formula Alternatively, the novel polymers ofFormula I above may also be obtained by the per se redistributionprocess of a linear siloxane having the formula Cl Si(OSiR C1 (IV) whereeach R is the same as defined above which comprises heating saidsiloxane at about 90 C. in the presence of a basic catalyst selectedfrom the group consisting of-phosphine oxides, amine oxides, or mixturesthereof, said catalysts having been described above. For example theredistribution of 1,1,1,7-tetrachlorohexamethylsiloxane (Formula III)above per so at 90 C. in the presence of (Me N) POalso produces a goodyield of linear 1,3,3,7- tetrachlorohexamethylsiloxane, Formula IIabove.

' The redistribution processes of this invention can also be carried outin the presence of an inert polar organic solvent having-a highdielectric constant, and such is often desirable, especially whencatalysts of low reactivity and/ or low reactive cyclics are employed,since these inert polar organic solvents also serve as cocatalyticagents for the redistribution. Suitable inert polar organic solvents arethose having a dielectric constant greater than 4, and preferablygreater than 10. Such compounds are Well known in the art and includehalogenated liquid hydrocarbons and ethers and especially polarcompounds having nitrogen present in their structure as nitrile groups,nitro groups,.and amide groups. Any high dielectric constant polarorganic compound may be used so long as it is inert, that-is, ,wontadversely interfere with the basic reac tion such as a hydroxycontaining compound might. Illus trativeexamples of such inert organicpolar compounds that-can be employedinclude, chloroform, bromoform,dichloromethane, iodomethane, dibromomethane, 1,1,1- trichloroethane,o-dibromobenzene, p-fiuorotoluene, methylbutyl ether, the dimethyl etherof ethylene glycol, tetrahydrofuran, 6,5-dichlorodiethylether,acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile,cyclohexonitrile, capronitrile, succinonitrile, ethoxyacetylene,pyridine, nitromethaue, nitroethane, nitropropane, nitrooctane,nitrobenzene, 'nitrotoluene, nitrocyclohexane, l-chloro-Z-nitrobenzene,formamide, acetamide, dimethylforrnamide, dimethylacetamide,tetramethylurea, ethyl carbalmate and the like. The preferred polarcompounds are acetonitrile and benzonitrile. The use of these inertorganic polar solvents are also often desirable when one wishes toobtain the best possible yield of specific linear Si or Si siloxanepolymer products. When employed the amount of inertpolar organiccompound will generally lie within the range of about 5 percent byweight up to about 25 percent by weight based on the combined weight ofsilicon reactants employed although higher amounts of polar compoundscan be used if desired. Of course, mixtures of said inert polar organiccompounds can be employed if desired. Moreover, conventionalnon-catalytic solvents such as aliphatic or aromatic hydrocarbons likehexane, benzene, toluene, xylene and the like as well as mixturesthereof may be used instead of the inert polar solvents mentioned aboveor in conjunction with said polar solvents.

Still another novel feature of the instant invention is the productionof novel linear substituted hydrocarbon siloxanes of the formula where Ris the same as defined above and x is 2 or 3, and R is a substitutedalkylene radical such as betacyanoethyl, gammacyanopropyl,omegacyanobutyl, betachloroethyl, gammachloropropyl, gammabromopropyl,gammamethoxypropyl, omegamethoxybutyl and the like. [For example, theredistribution reaction of about a 1:1 mole ratio ofgamma-chloropropylmethyldichlorosilane with hexamethyltrisiloxane atabout room temperature in the catalytic presence of (Me N) PO andacetonitrile produces a good yield of a linear 1-gammachloropropyl-1,7-dichloro-hexamethylsiloxane polymer of the formula (CH (Cl) (CICH CH CHSiO (Si(CH O Si(CH C1 The instant invention provides a means forintroducing chlorine functionality into linear siloxane polymers as wellas method for producing high yields of specific chlorosiloxane polymers.The chlorosiloxane polymer products have a wide range of utility wellknown in the organosilicon art. For example, their use in thepreparation of precise heat curable silicone resins and elastomers iswell known. They can also be used as cross-linking agents or roomtemperature vulcanizable resins or rubber systems. In addition they canbe employed as intermediates for producing a multitude of diiferentfunctional siloxane polymers of high molecular weight, for instance theycan be converted to alkoxy, acyloxy, hydroxy, containing siloxanepolymers and they can also be used to produce amino end-blockedsiloxanes, as shown for example by Union Carbides copending US. patentapplication Ser. No. 672,445, filed Oct. 3, 1967.

The following examples are illustrative of the present invention and arenot to be regarded as limitative. It is to be understood that all parts,percentages and proportions referred to herein and in the appendedclaims are by weight unless otherwise indicated. The symbols Me, Et, Pr,Bu, Vi and represent the methyl, ethyl, n-propyl, n-butyl, vinyl andphenyl radicals.

EXAMPLE 1 A solution composed of about 148.3 grams (0.5 mole) ofoctamethylcyclotetrasiloxane, about 129 grams (1.0 mole) ofdimethyldichlorosilane, about 4.0 grams (0.0014 mole) oftriphenylphosphine oxide and ml. of acetonitrile was brought to 65 C.and allowed to rise to 75 C. over 16.25 hours at which time vapor phasechromatographic analysis showed unreacted octamethylcyclotetrasiloxane,some chlorine endblocked tetrasiloxane, and an appreciable amount oflinear chlorine endblocked pentasiloxane, the desired product. Theacetonitrile and unreacted dimethyldichlorosilane was stripped at a pottemperature of 60 C./20 mm. and the precipitated catalyst filtered off.About 172.5 grams of linear chlorine endblocked siloxane liquid wasrecovered indicating a 38 percent conversion to product, the majoramount of which was linear 1,9 dichlorodecamethylpentasiloxane havingthe formula Cl(CH SiO [Si(CH O] 'Si(CH C1 EXAMPLE 2 A solution of about148.3 grams (0.5 mole) of octamethylcyclotetrasiloxane, about 97.0 grams(0.75 mole of dirnethyldichlorosilane, about 4.0 grams (0.018 mole) oftri-n-butylphosphine oxide and about 50 ml. of acetonitrile was broughtto reflux at 76 C. which rose to 87.5 C. over 6.67 hours. Theacetonitrile and excess dirnethyldichlorosilane were removed at a pottemperature of 50 C./20 mm. About 225.8 grams of linear chlorineendblocked siloxane fluid was obtained. Vapor phase chromatographyanalysis of the product mixture showed it to be composed primarily of 73percent of desired linear 1,9- dichlorodecamethylpentasiloxane alongwith about 17 percent of 9 percent of Cl CH SiOSi(CH C1 and a smallamount of Cl(CH SiOSi(CH OSi(CH C1 Similar results may be obtained byreplacing acetonitrile with other solvents such as, benzonitrile,propionitrile, acrylonitrile, bisbetachloroethyl ether, methylenechloride, chloroform, cyclohexanone, 1,1,2 trichloroethane,dimet'hylformamide, N-methylpyrrolidine and the like.

EXAMPLE 3 A solution composed of about 2.23 grams (0.01 mole) ofhexamethylcyclotrisiloxane, about 1.23 ml. (0.01 mole) ofdirnethyldichlorosilane, about 0.7 ml. (0.013 mole) of acetonitrile andabout 0.14 gram (0.0005 mole) of n-butyldiphenylphosphine oxide was heldat room temperature (about 23 C.) for one-half hour. Vapor phasechromatography analysis of the product showed a 90 percent yield ofdesired linear 1,7-dichlorooctamethyltetrasiloxane polymer having theformula A solution composed of about 3.0 ml. (0.0096 mole) ofoctamethylcyclotetrasiloxane, about 1.3 ml. (0.0107 mole) ofdimethyldichlorosilane, about 0.75 ml. (0.014) of acetonitrile and about0.1 gram (0.0013 mole) of pyridine N-oxide was refluxed for twentyhours. Vapor phase chromatography analysis showed the product mixture toconsist of 80 percent of desired linear dichlorodecamethylpentasiloxaneand 20 percent of higher molecular weight chloroendblocked siloxanes.

A second solution composed of about 2.23 grams (0.01 mole) ofhexamethylcyclotrisiloxane, about 1.3 ml. 0.0107 mole)) ofdirnethyldichlorosilane, about 0.75 ml. (0.0146 mole) of acetonitrile,and about 0.1 gram (0.0013 mole) of pyridine N-oxide Was held for onehour at 20 C. and then reacted for an additional hour at reflux. Vaporphase chromatography analysis showed a 95 percent yield of desiredlinear 1,7-dichlorooctamethyltetrasiloxane.

EXAMPLE 5 A solution composed of about 2.23 grams (0.01 mole) ofhexamethylcyclotrisiloxane, about 1.31 grams (0.0101 mole) ofdirnethyldichlorosilane, about 0.9 ml. (0.017 mole) of acetonitrile, and0.1 gram (0.00081 mole) of 2,6-dimethylpyridine N-oxide was reacted atreflux for eight hours. Vapor phase chromatography analysis of thereaction mixture showed a 95 percent yield of desired linear1,7-dichlorooctamethyltetrasiloxane.

EXAMPLE 6 A solution composed of about 670 grams (3.02 moles) ofhexamethylcyclotrisiloxane, about 362 ml. (387 grams, 3.0moles) ofdirnethyldichlorosilane, about 315 ml. (1246 grams, 6.0 moles) ofacetonitrile and about 13 grams (0.12 mole) of gamma-picoline N-oxidewas refluxed for two hours until a constant temperature was reached.

Time (min.): Temperature C.) 3 30 84 60 ""86 120 86 with x representing0, 1, 3, 4 and 5; and 97.3 percent of desired linear1,7-dichlorooctamethyltetrasiloxane. The yield of linear chlorineendblocked siloxanes was 987 grams or 93.2% of theoretical.

EXAMPLE 7 A solution composed of about 120ml. (129grams, 1.0 mole) ofdirnethyldichlorosilane, about 20.2 ml. of nundecane for an internalvapor phase chromatographic standard, about 308 ml. (296 grams, 1.0mole) of octamethylcyclotetrasiloxane and about 105 ml. (82 grams, 2moles) of acetonitrile and brought to reflux (about C.) at which time7.0 cc. (7.2 grams, 0.04 mole) of hexamethylphosphoramide [(CH N) PO]catalyst was added. The course of the reaction was observed byperiodically removing 1 cc. samples which were then diluted with 5 cc.of benzene and analyzed by vapor phase chromatography. In 210 minutesthe reaction had proceeded to a 47.3 percent conversion to linearchlorine endblocked siloxanes with a selectivity ratio of percent ofdesired linear 1,9 dichlorodecamethylpentasiloxane. The formula for theselectivity ratio is [the number of moles of unreactedoctamethyltetracyclicsiloxane plus the number of moles of desired linear1,9-dichlorodecamethylpentasiloxane produced divided by the number ofmoles of octamethyltetracyclicsiloxane starting material] multiplied by100. On setting over the weekend at ambient temperature (about 23 C.)the conversion of the reaction mixture increased to 61.1 percent with aselectivity for desired linear 1,9-dichlorodecamethylpentasiloxane of 87percent. The minor chloroendblocked siloxane products consisted of about5.7 percent of Cl(CH SiO[Si(CH O],,Si(CH Cl where x represents 0, 1 and2.

EXAMPLE 8 A solution composed of about 222.3 grams (1 mole) ofhexamethylcyclotrisiloxane, about 191.6 grams (1 mole) ofgrarnmachloropropylmethyldichlorosilane, about 8.3 grams ofhexamethylphosphoramide and about 45.5 grams of acetonitrile werestirred at room temperature for about 1.3 hours. The product mixture wasfractionally distilled and vapor phase chromatography analysis showedthe desired linear siloxane product to be1,7-dichloro-l-gammachloropropylheptamethyltetrasiloxane having theformula A series of six runs produced an average 88.7 mole percent yield(about 737 grams) of said desired product which had a boiling point ofabout 295 C./760 mm.

Other substituted hydrocarbon endblocked linear siloxanes can besimilarly produced by employing in place of the above silane other-silane reactants such as, betacyanoethylmethyldichlorosilane,gammacyanopropylmethyldichlorosilane,omegacyanobutylmethyldichlorosilane,betachloroethylmethyldichlorosilane,gammabromopropylmethyldichlorosilane,gammamethoxypropylmethyldichlorosilane,omegarnethoxybutylmethyldichlorosilane and. the like and/or by replacingthe above tri cyclosiloxane with a tetracyclosiloxane such asoctamethylcyclotetrasil'oxane and the like.

EXAMPLE 9 A'solution of about 1.0 ml. of (0.007 mole) ofdimethyldichlorosilane, about 2.23 grams (0.01 mole) ofhexamethylcyclotrisiloxane, about 0.75 ml. (0.014 mole) of 'acetonitrileand about 0.1 ml. (0.005 mole) of hexamethylphosphoramide was refluxedfor one hour at which time vapor phase chromatography analysis showed abetter than 95 percent yield of linear1,7-dichlorooctamethyltetrasiloxane. I EXAMPLE 10 A solution composed ofabout 0.5 gram (0.0022 mole) linear 1,7dichloro-l,1-diphenylhexamethyltetrasiloxane where represents a phenylradical.

EXAMPLE 13 Following the procedures described in the above examples forthe process of this invention other linear chloroendblocked siloxanescan be prepared by reacting at reflux at least one mole of thechlorosilane monomer with at least one mole of the diorganocyclic in thepresence of a catalytic amount of phosphine oxide and/or amine oxidecatalyst as shown by the following illustraofhexamethylcyclotrisiloxane, about 0.3 ml. (0.0024 15 tive table.

mole) of dimethyldichlorosilane, about 0.4 ml. (0.0076 mole) ofacetonitrile, about 3.0 ml. (0.028 mole) of toluene, and about 1.1 grams(0.002 mole) of a -'complex was reacted for one-half hour at roomtemperature (about C.) to produce a 95 percent yield of 60 C./20 mm.followed by filtration to remove the prec ipitated catalyst yielded175.6 grams of linear chlorine endblocked siloxanes representing a 42percent conversion. Vapor phase chromatography showed the principalproducts to be linear 1,7-dichlorooctamethyltetrasiloxane and linear1,9-dichlorodecamethylpentasiloxane in a 1:4 ratio respectively.

- EXAMPLE 12 A solution composed of about 111.2 grams (0.5 mole) ofhexamethylcyclotrisiloxane, about 126.6 grams (0.5 mole) ofdiphenyldichlorosilane, about 4.0 grams (0.018 mole) oftri-n-butylphosphine oxide and about 50 ml. of acetonitrile was held at91 to 93 C. for 17.5 hours. Vapor phase chromatographic analysis showedcomplete consumption of the cyclotrisiloxane in the presence of. a traceof 1,3-dichlorotetramethylsiloxane of the formula Cl (CH SiOSi (CH C1and the major product consisting essentially of desired In the abovetable the symbol Me represents a methyl radical (-CH Et represents anethyl radical (-C H Bu represents a n-butyl radical (-C H Vi representsa vinyl radical (CH CH and represents a phenyl radical (C H EXAMPLE 14 Asolution composed of about 224.5 grams of hexamethylcyclotrisiloxane,about 120 ml. of tetrachlorosilane, about 3.4 grams of triphenylphosphine oxide and about 200 ml. of benzene were allowed to react atroom temperature overnight. Vapor phase chromatography showed theproduct to be comprised primarily (about percent) of desired linear1,1,1,7-tetrachlorohexamethyltetrasiloxane having the formula Theproduct was then heated at about 90 C. for two hours to convert theinitial linear 1,1,1,7-tetrachlorohexamethyltetrasiloxane into desiredlinear 1,3,3,7-tetrach1orohexamethyltetrasiloxane having the formula.

which was recovered by vapor phase chromatography distillation. Thestructure of said linear 1,3,3,7--tetrach1orohexamethyltetrasiloxane wasunequivocally determined by converting an aliquot of it to its fluoroanalog with and running a nuclear magnetic resonance test on both theehloro and fiuoro analogs of said siloxane.

EXAMPLE 15 A solution composed of about 224.5 grams ofhexamethylcyclotrisiloxane, about ml. of tetrachlorosilane, about 3.4grams of triphenylphosphine oxide and about 200 ml. of benzene weredirectly reacted at about 90 C. for two hours to produce about a 95percent yield of desired linear1,3,3,7-tetrachlorohexamethyltetrasiloxane which product was establishedby a nuclear magnetic resonance test as outlinedin Example 14; 1

Various modifications and variations of this invention will be obviousto a worker skilled in the art and it is understood that suchmodifications and variations are to be included within the purview ofthis application and the spirit and scope'of the appended claims.

What is claimed is:

1. A process for preparing chloro substituted linear polysiloxanes whichcomprises interacting, in the presence of a catalytic amount of acatalyst selected from the group consisting of phosphine oxides, amineN-oxides, and mixtures thereof, (A) an organocyclosiloxane of theformula or mixtures thereof, wherein each R is a radical independentlyselected from the group consisting of hydrogen, an unsubstitutedmonovalent hydrocarbon radical having from 1 to 18 carbon atoms and asubstituted monovalent hydrocarbon radical having from 1 to 18 carbonatoms, and :wherein n is an integer of 3 or 4; with (B) a chlorosubstituted silane of the formula or mixtures thereof, wherein each R isthe same as defined above and wherein m has a value of from to 3inclusive; whereby the cyclosiloxane (A) forms a linear siloxane polymerhaving attached to one terminal silicon atom a chlorine atom from thesilane (B) and having attached to its other terminal silicon atomthrough a siloxane linkage the silicon atom of the silane from which thechlorine atom separated.

2. A process as defined in claim 1 wherein each R radical of theorganocyclosiloxane reactant is a radical independently selected fromthe group consisting of methyl, ethyl, vinyl and phenyl radicals;wherein each R radical of the chlorinated silane reactant is a radicalindependently selected from the group consisting of methyl, ethyl,vinyl, phenyl, betacyanoethyl, gammacyanopropyl, omegacyanobutyl,betachloroethyl, gammachloropropyl, betabromoethyl, gammabromopropyl,gammamethoxypropyl and omegamethoxybutyl radicals, and wherein a polarsolvent is also present during the reaction.

3. A process as defined in claim 2 wherein m represents the integer 2and wherein the catalyst employed is a phosphine oxide selected from thegroup consisting of wherein each R radical of the oxide is independentlyselected from the group consisting of alkyl having from 1 to 18 carbonatoms and dimethylamino radicals.

4. A process as defined in claim 2 wherein m represents the integer 2and wherein the catalyst employed is an amine oxide having the formulawherein each R is independently a monovalent hydrocarbon radical havingfrom 1 to 8 carbon atoms or wherein R and N taken together form apyridine radical.

5. A process as defined in claim 3, wherein the organocyclosiloxanereactant is hexamethyltrisiloxane and the chloro substituted silanereactant is dimethyldichlorosilane.

6. A process as defined in claim 4, wherein the organocyclosiloxanereactant is hexamethylcyclotrisiloxane and the chloro substituted silanereactant is dimethyldichlorosilane.

7. A process as defined in claim wherein the phosphine oxide is selectedfrom the group consisting of triphenylphosphine oxide,trim-butylphosphine oxide and hexamethylphosphoramide, and wherein thepolar solvent is selected from the group consisting of acetonitrile,benzonitrile, propionitrile, acrylonitrile, 1,2-dimethoxyethane,chloroform, bis-betachloroethylether, cyclohexanone andmethylenechloride. v

8. A process as defined in claim 6, wherein the amine oxide is selectedfrom the group consisting of pyridine N-oxide, Z-methylpyridine N-oxide,4-methylpyridine N- oxide and 2,6-dimethylpyridine N-oxide and whereinthe polar solvent is selected from the group consisting of acetonitrile,benzonitrile, propionitrile, acrylonitrile, 1,2-dimethoxyethane,chloroform, bis betachloroethylether, cyclohexanone, andmethylenechloride.

9. A process as defined in claim 3 wherein the organocyclosiloxanereactant is octame'thyltetrasiloxane and the chloro substituted silanereactant is dimethyldichlorosilane.

10. A process as defined in claim 4, wherein the organocyclosiloxanereactant is octamethyltetrasiloxane and the chloro substituted silanereactant is dimethyldichlorosilane.

11. A process as defined in claim 9 wherein the phosphine oxide isselected from the group consisting of triphenylphosphine oxide,trim-butylphosphine oxide and hexamethylphosphoramide, and wherein thepolar solvent is selected from the group consisting of acetonitrile,benzonitrile, propionitrile, acrylonitrile, 1,2-dimethoxyethane,chloroform, bis-betachloroethylether, cyclohexanone, andmethylenechloride.

12. A process as defined in claim 10, wherein the amine oxide isselected from the group consisting of pyridine N-oxide, 2-methylpyridineN-oxide, 4-methylpyridine.N- oxide and 2,6-dimethylpyridine N-oxide andwherein the polar solvent is selected from the group consisting ofacetonitrile, benzonitrile, propionitrile, acrylonitrile, 1,2-dimethoxyethane, chloroform, bis-betachloroethylether, cyclohexanone andmethylenechloride.

13. A process as defined in claim 1 wherein the organocyclosiloxanereactant is hexamethylcyclotrisiloxane and wherein the chlorosubstituted silane reactant is tetrachlorosilane.

14. A process for preparing linear 1,9-dichlorodecamethylpentasiloxanewhich comprises interreacting in the presence of a catalytic amount oftriphenylphosphine oxide and an acetonitrile solvent, (A)octamethylcyclotetrasiloxane with (B) dimethyldichlorosilane.

15. A process for preparing linear 1,9-dichlorodecamethylpentasiloxanewhich comprises interreacting in the presence of a catalytic amount oftri-n-butylphosphine oxide and an acetonitrile solvent, (A)octamethylcyclotetrasiloxane with (B) dimethyldichlorosilane.

16. A process for preparing linear 1,9-dichlorodecamethylpentasiloxanewhich comprises interreacting in the presence of a catalytic amount ofpyridine N-oxide and an acetonitrile solvent, (A)octamethylcyclotetrasiloxane with (B) dimethyldichlorosilane.

17. A process for preparing linear 1,9-dichl0rodecamethylpentasiloxanewhich comprises interreacting in the presence of a catalytic amount ofhexamethylphosphoramide and an acetonitrile solvent, (A)octamethylcyclotetrasiloxane with (B) dimethyldichlorosilane.

18. A process for preparing linear 1,7-dichloro-1,1-diphenylhexamcthyltetrasiloxane which comprises interreacting in thepresence of a catalytic amount of tri-nbutylphosphine oxide and anacetonitrile solvent, (A) hexamethylcyclotrisiloxane with (B)diphenyldichlorosilane.

19. A process for preparing linear1,7-dichloro-lgammachloropropylheptame'thyltetrasiloxane which comprisesinterreacting in the presence of a catalytic amount ofhexamethylphosphoramide and an acetonitrile solvent, (A)hexamcthylcyclotrisiloxane with (B)gammachloropropylmethyldichlorosilane.

20. A process for preparing linear 1,7-dichlorooctamethyltetrasiloxanewhich comprises interreacting in the presence of a catalytic amount ofn-butyldiphenylphosphine oxide and an acetonitrile solvent (A)hexamethylcyclotrisiloxane with (B) dimethyldichlorosilane.

21. A process for preparing linear 1,7-dichlorooctamethyltetrasiloxanewhich comprises interreacting in the presence of a catalytic amount ofpyridine N-oxide and an acetonitrile solvent (A)hexamethylcyclotrisiloxane with (B) dimethyldichlorosilane.

22. A process for preparing linear 1,7-dichlorooctamethyltetrasiloxanewhich comprises interreacting in the presence of a catalytic amount ofhexamethylphosphoramide and an acetonitrile solvent, (A) hexamethylcyclmtrisiloxane with (B) dimethyldichlorosilane.

23. A process for preparing linear1,l,1,7-tetrachlorhexamethyltetrasiloxane which comprises interreactingat about room temperature in the presence of a catalytic amount oftriphenylphosphine oxide and a benzene sol vent (A)hexamethylcyclotrisiloxane with (B) tetrachlorosilane.

24. A process for preparing linear1,3,3,7-tetrachlorohexamethyltetrasiloxane which comprises interreactingat about 90 C. in the presence of a catalytic amount oftriphenylphosphine oxide and a benzene solvent (A)hexamethylcyclotrisiloxane with (B) tetrachlorosilane.

25. A linear chloro-endblocked siloxane having the general formulawherein Me represents a methyl radical; wherein n is an integer of from2 to 4 inclusive and wherein X is a member selected from the groupconsisting of cyano, chlorine, bromine and methoxy radicals and x is aninteger of 2 or 3 inclusive.

References Cited UNITED STATES PATENTS 3,162,662 12/1964 Brown et a1.260-4482 3,235,579 2/1966 Brown et a1. 260-4482 TOBIAS E. LEVOW, PrimaryExaminer W. F. W. BELLAMY, Assistant Examiner U.S. Cl. X.R.

